The present invention generally relates to shielded containers for the handling of radioactive materials and, more particularly, to radiation-resistant shields allowing improved handling of radioactive materials used in the health care industry.
In the health care industry and more specifically in the filed of nuclear medicine, radioactive materials known as radiopharmaceuticals are used in various applications, including non-intrusive imaging of patients for various diagnostic as well as therapeutic purposes. Over the years, the health care industry has developed many different radiopharmaceuticals designed to facilitate such applications. Radiopharmaceuticals are generally used in a liquid form suitable for injection into a patient via standard 3 cc or 5 cc hypodermic syringes.
Because of the radioactive nature of radiopharmaceuticals, they should be handled carefully and various governmental agencies, including the U.S. Department of Transportation, the Nuclear Regulatory Commission, and the Occupational Health and Safety Administration have promulgated regulations for safe handling of such materials. In addition to the radioactivity of the radiopharmaceutical, the biologically contaminated needle of the used syringe can pose a risk to disposal workers. To avoid some of the overhead costs associated with addressing the above concerns, many hospitals have resorted to outside pharmacy companies having expertise in the compounding and handling of radiopharmaceuticals.
Typically, health care providers order radiopharmaceuticals in syringes containing an individual dose for a specific patient. Methods and apparatus for safe handling of syringes containing conventional radiopharmaceuticals have been developed. For example, a system for transporting syringes containing radiopharmaceuticals is disclosed in U.S. Pat. Nos. 5,519,931 and 5,536,945.
One type of imaging process that has received increasing attention in the health care industry is known as positron emission tomography ("PET"). In general, the PET process involves the use of a radiopharmaceutical labeled with a positron-emitting isotope, administered intravenously to a patient. Cyclotron machines are used to produce PET isotopes, which can be highly radioactive. After injection of the PET radiopharmaceutical, a PET scanner can image the distribution of the PET radiopharmaceutical in the area of interest within the patient's body. As is well known, the PET imaging process can yield superior results as compared to conventional nuclear medicine imaging techniques.
Because PET radiopharmaceuticals can be much more radioactive than conventional radiopharmaceuticals, conventional handling techniques are not well suited for the effective transport and handling of PET radiopharmaceuticals. To address this problem, transportation containers with massive lead shields have been used as transport containers. These heavy containers, weighing well over 100 pounds, are not easily moved and handled, thereby making compounding and delivery of PET radiopharmaceuticals extremely difficult from a logistical standpoint. For example, because PET radiopharmaceuticals have very short half lives, some on the order of 20 minutes, the use of massive lead shields and massive transportation containers does not facilitate the quick handling required to distribute these radiopharmaceuticals before they decay.
Another drawback is related to the handling of the PET isotopes and radiopharmaceuticals during compounding. In particular, pharmacists use what is known as a "drawing station" to fill a syringe from a standard septum-topped vial containing PET radiopharmaceutical or PET isotope. One conventional drawing station has a massive lead shield that is pivotally mounted between opposing arms projecting upwardly from a base. The vial is delivered to the drawing station in a small tungsten insert that is placed into a cavity in the lead shield, which, by manually turning a crank, can be rotated to hold the vial in an inverted position. Once in the inverted position, a syringe needle can be inserted upward through the septum of the vial and the syringe can draw the PET radiopharmaceutical from the vial. The syringe is held within a shield that twists onto the drawing station to shield the syringe during the drawing process.
While the PET drawing station described above has been generally satisfactory, it has many drawbacks. For example, the lead shield is very massive and it is difficult for health care workers to rotate it during the drawing process. Another drawback is related to the tungsten insert, which does not shield radiation as well as the lead shield into which it is inserted. Thus, during the time that the insert is not within the massive lead shield, more radiation is emitted from the insert than would escape from the lead shield. Another drawback is that the insert exposes the vial during the drawing process, thereby allowing unwanted radiation exposure.
Yet another drawback is related to the twist-on mounting mechanism that allows the syringe shield to be joined with the drawing station. During the time required for health care workers to align the twist-on mechanism on the syringe shield with its corresponding receiving structure on the drawing station, unwanted radiation exposure can occur. Further, if the alignment process takes more than a few minutes, the PET isotope will have lost a significant amount of radioactivity due to the PET isotope's short half life.
After the drawing process is completed, the syringe containing the PET radiopharmaceutical is delivered to the patient for injection. One conventional radiopharmaceutical transportation container has a twist-on cap that mates with a housing to hold a syringe therein. While this container is generally acceptable for less radioactive radiopharmaceuticals, it has certain drawbacks when used with highly radioactive PET radiopharmaceuticals. One such drawback is that this transportation container permits radiation exposure when the container is opened to allow access to the syringe held therein. Yet another drawback is associated with the mechanism that is used to hold the cap to the housing. In particular, there is radiation exposure from the container during the time required to screw the cap to the housing.
Accordingly, there exists a need for an improved drawing station system for handling radioactive materials used in compound nuclear medicines. The present invention satisfies this need and provides further related advantages.